The present invention relates to a memory package system in which data is exchanged between a memory module and a write/read unit by contactless induction coupling.
In U.S. patent application Ser. Nos. 07/048832 and 07/053759, the inventors of the present invention have proposed systems in which in order to write and read data by a write/read unit into and from a non-volatile memory, e.g., an EEPROM provided in a memory module in a contactless manner, induction coils are assembled into the write/read unit and memory module. In the writing or reading mode, both induction coils are disposed so as to face each other at a predetermined gap interval, and an operating electric power is supplied to the memory module and the write/read data is serially transmitted into/from the memory module by the resultant electromagnetic induction coupling.
According to the power supply to the memory module and the data transmission for writing or reading by such a contactless induction coupling system, when the number of kinds of signals increases, the number of induction coils which are provided for the write/read unit and memory module also increases. To solve this problem, the systems disclosed in U.S. patent application Ser. Nos. 07/048832 and 07/053759 use a start-stop communication system in which there is no need to transmit transmission/reception sync clocks (shift clocks) as a communication system for transmitting serial data and converting into parallel data. Namely, according to the start-stop communication system, it is sufficient to transmit between the write/read unit and the memory module three kinds of signals: a power source signal which is sent from the write/read unit to the memory module; an up-signal to write or read; and a down-signal serving as a read data which is returned from the memory module to the write/read unit.
As mentioned above, since the number of kinds of transmission signals can be reduced to three, the start-stop communication system has an advantage in that the number of induction coils which are used to couple the write/read unit with the memory module in a contactless induction coupling manner can be reduced. However, according to this system, a communication controller for the start-stop communication control, which is known as an USART, needs to be provided in each of the write/read unit and memory module. In this kind of memory package system, it is desired to miniaturize the memory module. However, the start-stop communication system has a problem in that the memory module increases in size by an amount corresponding to the size of the communication controller (USART).
Additionally, the start-stop communication system synchronizes the shift clocks reproduced from the reception signal with the received data bits and converts the received serial data into the parallel data, so that data errors are likely to occur as compared with the case where the transmission/reception sync clocks are used. Consequently, this system certainly requires an error control such as a parity check or the like and when errors were detected, a request for retransmission is repeatedly generated until the correct data can be received, so that the communication time to write and read is prolonged.